In a conventional film winding device for a camera, the amount of film wound up has been controlled by counting the number of perforations formed in a film.
A practical prior art method for detecting the perforations is as follows:
A reflective photointerrupter is disposed on one side, and a black member for absorbing the light emitted by the photointerrupter is disposed on the other side of the film in such a way that the reflective photointerrupter and the black member sandwiches the perforations formed in a film.
Further, the light emitted from a light emitting diode is reflected by or transmitted through a series of film perforations, and received by a light receiving element to detect the film perforations, whenever the film perforations are passed between the reflective photointerrupter and the black member.
The film loading error and the ends of film winding-up operation and film rewinding operation have been detected so far by counting the number of perforations formed in the film.
A prior art method of detecting a film loading error is as follows:
When a film is loaded in a camera and then a rear lid is closed, the film is wound up by three frames. In this film winding-up operation by three frames, when the detection signals of the photointerrupter for detecting the film perforations are not generated continuously for a predetermined time, a film loading error is detected by determining that the film is not wound up correctly.
The prior art method for detecting the ends of the film winding-up and film rewinding operation is as follows:
When the film is being wound up or rewound, the detection signals of the photointerrupter for detecting the film perforations are to be generated in unison with the film feeding operation. However, when the film winding-up operation ends, the detection signals are not generated from the photointerrupter. Therefore, when the detection signals are not generated continuously beyond a predetermined time, the end of the film winding-up or rewinding operation is determined.
In the prior art method for detecting a film loading error and the end of film winding-up or rewinding operation, as described above, since a photointerrupter and other elements are used, there exist various problems in that the number of parts is large; the cost thereof is high; and the size thereof is large because the photointerrupter is large in size and therefore it is difficult to house these elements in a subminiature camera.
In addition, since the amount of film winding-up is not directly detected as described above, when the amount of film winding is controlled by the amount of rotation of the motor, there exists a problem in that it is not impossible to simply control the amount of film winding on the basis of the rotation of the motor, because the amount of film winding for each separate motor rotation is different, depending upon the amount of film already wound up.